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13 * software distributed under the License is distributed on an *
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY *
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16 * specific language governing permissions and limitations *
17 * under the License. *
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19
20
21
22 package org.apache.james.util.stream;
23
24 import java.io.IOException;
25 import java.io.InputStream;
26
27 /**
28 * An InputStream class that terminates the stream when it encounters a
29 * particular byte sequence.
30 *
31 * @version 1.0.0, 24/04/1999
32 */
33 public class CharTerminatedInputStream
34 extends InputStream {
35
36 /**
37 * The wrapped input stream
38 */
39 private InputStream in;
40
41 /**
42 * The terminating character array
43 */
44 private int match[];
45
46 /**
47 * An array containing the last N characters read from the stream, where
48 * N is the length of the terminating character array
49 */
50 private int buffer[];
51
52 /**
53 * The number of bytes that have been read that have not been placed
54 * in the internal buffer.
55 */
56 private int pos = 0;
57
58 /**
59 * Whether the terminating sequence has been read from the stream
60 */
61 private boolean endFound = false;
62
63 /**
64 * A constructor for this object that takes a stream to be wrapped
65 * and a terminating character sequence.
66 *
67 * @param in the <code>InputStream</code> to be wrapped
68 * @param terminator the array of characters that will terminate the stream.
69 *
70 * @throws IllegalArgumentException if the terminator array is null or empty
71 */
72 public CharTerminatedInputStream(InputStream in, char[] terminator) {
73 if (terminator == null) {
74 throw new IllegalArgumentException("The terminating character array cannot be null.");
75 }
76 if (terminator.length == 0) {
77 throw new IllegalArgumentException("The terminating character array cannot be of zero length.");
78 }
79 match = new int[terminator.length];
80 buffer = new int[terminator.length];
81 for (int i = 0; i < terminator.length; i++) {
82 match[i] = (int)terminator[i];
83 buffer[i] = (int)terminator[i];
84 }
85 this.in = in;
86 }
87
88 /**
89 * Read a byte off this stream.
90 *
91 * @return the byte read off the stream
92 * @throws IOException if an IOException is encountered while reading off the stream
93 * throws ProtocolException if the underlying stream returns -1 before the terminator is seen.
94 */
95 public int read() throws IOException {
96 if (endFound) {
97 //We've found the match to the terminator
98 return -1;
99 }
100 if (pos == 0) {
101 //We have no data... read in a record
102 int b = in.read();
103 if (b == -1) {
104 //End of stream reached without seeing the terminator
105 throw new java.net.ProtocolException("pre-mature end of data");
106 }
107 if (b != match[0]) {
108 //this char is not the first char of the match
109 return b;
110 }
111 //this is a match...put this in the first byte of the buffer,
112 // and fall through to matching logic
113 buffer[0] = b;
114 pos++;
115 } else {
116 if (buffer[0] != match[0]) {
117 //Maybe from a previous scan, there is existing data,
118 // and the first available char does not match the
119 // beginning of the terminating string.
120 return topChar();
121 }
122 //we have a match... fall through to matching logic.
123 }
124 //MATCHING LOGIC
125
126 //The first character is a match... scan for complete match,
127 // reading extra chars as needed, until complete match is found
128 for (int i = 0; i < match.length; i++) {
129 if (i >= pos) {
130 int b = in.read();
131 if (b == -1) {
132 //end of stream found, so match cannot be fulfilled.
133 // note we don't set endFound, because otherwise
134 // remaining part of buffer won't be returned.
135 return topChar();
136 }
137 //put the read char in the buffer
138 buffer[pos] = b;
139 pos++;
140 }
141 if (buffer[i] != match[i]) {
142 //we did not find a match... return the top char
143 return topChar();
144 }
145 }
146 //A complete match was made...
147 endFound = true;
148 return -1;
149 }
150
151 /**
152 * Private helper method to update the internal buffer of last read characters
153 *
154 * @return the byte that was previously at the front of the internal buffer
155 */
156 private int topChar() {
157 int b = buffer[0];
158 if (pos > 1) {
159 //copy down the buffer to keep the fresh data at top
160 System.arraycopy(buffer, 1, buffer, 0, pos - 1);
161 }
162 pos--;
163 return b;
164 }
165 }
166